(1) Field of the Invention
The present invention relates to an accounting system in a network, such as a B-ISDN (Broad band Integrated Services Digital Network), for offering video programs.
(2) Description of Related Art
Recently, a B-ISDN has been studied actively. As the B-ISDN has broad band characteristics, using the B-ISDN for offering video programs in, for example, CATV (Cable Television) service is a promising pursuit.
In a conventional CATV service, an accounting system as shown in FIG. 1 is used. Referring to FIG. 1, a plurality of CATV terminals 44a, 44b and 44c are coupled to a network 40 by coaxial cables, and the network 40 offers video programs in the CATV service to the CATV terminals 44a, 44b and 44c. The network 40 is provided with an accounting unit 41, account controllers 42a, 42b and 42c respectively coupled to the CATV terminals 44a, 44b and 44c, and timers 43a, 43b and 43c respectively connected to the account controllers 42a, 42b and 42c. The network 40 is also provided with a well known unit, not shown in FIG. 1, for transmitting pictures in video programs requested by the CATV terminals to the CATV terminals.
For example, the CATV terminal 44a transmits a transmission request of a video program desired by a user to the network 40 along with channel information of the video program. When receiving the transmission request, the network 40 transmits pictures in the video program in the specified channel. When the network 40 starts to transmit the pictures in the video program requested by the CATV terminal 44a, the timer 43a is activated and starts to count a time. The account controller 42a determines whether or not a channel changing information transmitted from the CATV terminal 44a is received before the timer 43a reaches n sec. (e.g. 300 sec.). When the account controller 42a receives the channel changing information, the timer 43a is reset and stars to count a time again. When the timer 43a reaches m sec. (e.g. 240 sec.) smaller than n sec. (m&lt;n) without receipt of the channel changing information, the account controller 43a transmits a notice signal so as to inform the user of the CATV terminal 44a that the account operation will start soon. When the CATV terminal 44a receives the notice signal, for example, a notice lamp provided therein is turned on. After this, when the timer 43a reaches n sec. without receipt of the channel changing information, a start signal is supplied from the account controller 42a to the accounting unit 41. The accounting unit 41 then starts the accounting operation. The account controller 42a transmits account start information to the CATV terminal 44 a.
In a case where the B-ISDN is used for offering video programs in the CATV service, various information may be transmitted between the B-ISDN and terminals in an ATM (Asynchronous Transfer Mode). In this case, functions for counting time and for transmitting the notice signal informing that the accounting operation will start soon, and other functions regarding the accounting operation must be added to the B-ISDN. As the number of subscriber in the B-ISDN is very large, the load, in the B-ISDN, concerning the accounting operation is increased.